Read oil about it …

2012-06-18 07:58

We take a lot of things for granted as motorcyclists. When we need to replace a tyre or perhaps the occasional battery we go to the ends of the earth for the best price to ensure we can continue motorcycling in a safe and proper manner.

When it comes to filling up the fuel tank we just pull on to the garage forecourt and top up with little thought about the quality of fuel or oil that’s going to be coursing through that mechanical marvel (the very expensive engine you have between your legs), so you can continue your journey.


In the case of oil – no matter which brand you buy or fuel company you prefer – it should always have an API rating (American Petroleum Institute). You’ll find it on the can or plastic bottle (if it just says multigrade, run a mile).

As an example, a can of Castrol GTX has an API-SL rating denoting it’s a 20W-50 multigrade. You have to remember that good oil costs fair money – but good oil is always going to be cheaper than a set of bearings and an untimely engine rebuild. Oil can never break down but it does become contaminated.

The slippery stuff is classified according to its viscosity, in other words a measure of its resistance to flow – in other words a thin, free-flowing oil has a low viscosity, a thick, slow-flowing oil a high viscosity. Viscosity ratings are given an SAE (Society of Automotive Engineers) number. This is applied to motorcycle crankcase and transmission oils (as we’re talking bikes), which come within a specified range of viscosities at a particular temperature.


Take, for instance, a 10W/40 oil (the W stands for winter) will have an SAE viscosity of 10 at -18°C and 40 at summer temperature (measured at 99°C). The lower the number the thinner the oil, so it stands to reason that in cold climes (have you ever been stuck in Harrismith, KZN in the middle of winter – I have, and that’s cold!), thin oil offers less resistance when your starter motor button is thumbed.

Conversely, in summer the oil takes on a thickening effect.

Certain current Suzuki models use the cooling role of oil to good effect in their GSX range of engines. In this instance oil is pumped at a faster rate through considerably more galleries and drillings than those that would be found on an air-cooled motor. The crankshaft, meanwhile, utilises oil jets to spray the underside of the pistons to provide further additional cooling to vital internals.

It’s worth mentioning – no matter what motorcycle you ride – that most engine damage occurs during engine start-up. High camshaft motors need to kept at little more than tick-over while warming up to avoid damage.


Maybe you’ve attended one of those crazy but fun motorcycle rallies where, for no apparent reason, in the middle of the night, some moron decides to wake everybody up by starting up his bike until it hits the rev limiter… assuming the motor doesn’t self-destruct first!

To sum up, buy the best oil you can afford – it’s an item you really can’t afford to be a skinflint about. Should you prefer to do your own oil changes be sure to dispose of your used oil in the correct manner. Your local garage or spares supplier should be able to help in this regard.

Last, but not least, be sure to wipe every trace of oil from your wife’s washing-up bowl…